4,565 research outputs found
Incentive Mechanisms for Motivating Mobile Data Offloading in Heterogeneous Networks: A Salary-Plus-Bonus Approach
In this paper, a salary-plus-bonus incentive mechanism is proposed to
motivate WiFi Access Points (APs) to provide data offloading service for mobile
network operators (MNOs). Under the proposed salary-plus-bonus scheme, WiFi APs
are rewarded not only based on offloaded data volume but also based on the
quality of their offloading service. The interactions between WiFi APs and the
MNO under this incentive mechanism are then studied using Stackelberg game. By
differentiating whether WiFi APs are of the same type (e.g. offloading cost and
quality), two cases (homogeneous and heterogeneous) are studied. For both
cases, we derive the best response functions for WiFi APs (i.e. the optimal
amount of data to offload), and show that the Nash Equilibrium (NE) always
exists for the subgame. Then, given WiFi APs' strategies, we investigate the
optimal strategy (i.e. the optimal salary and bonus) for the MNO to maximize
its utility. Then, two simple incentive mechanisms, referred to as the
salary-only scheme and the bonus-only scheme, are presented and studied using
Stackelberg game. For both of them, it is shown that the Stackelberg
Equilibrium (SE) exists and is unique. We also show that the salary-only scheme
is more effective in offloading more data, and the bonus-only scheme is more
effective in selecting premium APs (i.e. providing high-quality offloading
service at low cost), while the salary-plus-bonus scheme can strike a well
balance between the offloaded data volume and the offloading quality.Comment: Double-column, 13 Pages, 6 Figures. An extended work of the
conference version presented in IC
Riding on the Primary: A New Spectrum Sharing Paradigm for Wireless-Powered IoT Devices
In this paper, a new spectrum sharing model referred to as riding on the
primary (ROP) is proposed for wireless-powered IoT devices with ambient
backscatter communication capabilities. The key idea of ROP is that the
secondary transmitter harvests energy from the primary signal, then modulates
its information bits to the primary signal, and reflects the modulated signal
to the secondary receiver without violating the primary system's interference
requirement. Compared with the conventional spectrum sharing model, the
secondary system in the proposed ROP not only utilizes the spectrum of the
primary system but also takes advantage of the primary signal to harvest energy
and to carry its information. In this paper, we investigate the performance of
such a spectrum sharing system under fading channels. To be specific, we
maximize the ergodic capacity of the secondary system by jointly optimizing the
transmit power of the primary signal and the reflection coefficient of the
secondary ambient backscatter. Different (ideal/practical) energy consumption
models, different (peak/average) transmit power constraints, different types
(fixed/dynamically adjustable) reflection coefficient, different primary
system's interference requirements (rate/outage) are considered. Optimal power
allocation and reflection coefficient are obtained for each scenario.Comment: Submitted to IEEE Trans. Wireless Communication
Studying the molecule in the Bethe-Salpeter equation approach
We study the possible bound states of the system in the Bethe-Salpeter
(BS) formalism in the ladder and instantaneous approximations. By solving the
BS equation numerically with the kernel containing one-particle exchange
diagrams and introducing three different form factors (monopole, dipole, and
exponential form factors) at the vertices, we investigate whether the isoscalar
and isovector bound states may exist, respectively. We find that
could be accommodated as a molecule, whereas the
interpretation of as a molecule is disfavored. The bottom
analog of may exist but that of does not.Comment: 17 pages, 6 figures, and 4 table
Hadronic decays of in the perturbative QCD approach
We calculate the branching ratios and polarization fractions of the decays in the perturbative QCD(pQCD) approach at leading order, where
() stands for the axial-vector state. By
combining the phenomenological analyses with the perturbative calculations, we
find the following results: (a) the large decay rates around to
of the decays dominated by the longitudinal
polarization(except for the mode) are predicted and
basically consistent with those in the QCD factorization(QCDF) within errors,
which are expected to be tested by the Large Hadron Collider and Belle-II
experiments. The large branching ratio could provide
hints to help explore the mechanism of the color-suppressed decays. (b) the
rather different QCD behaviors between the and mesons result in the
destructive(constructive) contributions in the nonfactorizable spectator
diagrams with emission. Therefore, an interesting pattern of the
branching ratios appears for the color-suppressed and modes in the pQCD approach, , which is different
from in the QCDF and would be verified at future experiments. (c) the
large naive factorization breaking effects are observed in these decays. Specifically, the large nonfactorizable spectator(weak
annihilation) amplitudes contribute to the mode(s), which demand confirmations
via the precise measurements.Comment: 13 pages, 1 figure, 5 tables, revtex fil
Studying the bound state of the system in the Bethe-Salpeter formalism
In this work, we study the molecule in the Bethe-Salpeter (BS)
equation approach. With the kernel containing one-particle-exchange diagrams
and introducing two different form factors (monopole form factor and dipole
form factor) in the vertex, we solve the BS equation numerically in the
covariant instantaneous approximation. We investigate the isoscalar and
isovector systems, and we find cannot be a
molecule
Plasmonic Crystal Cavity on Single-Mode Optical Fiber End Facet for Label-Free Biosensing
All surface plasmon resonance (SPR) devices on single-mode optical fibers'
(SMF) end facets, as reported up to date, are limited by severely broad and
shallow resonance spectra. The consequent poor performance when they are used
as refractive index sensors, together with the challenge of nanofabrication on
fiber end facets, has prohibited the development of such devices for label-free
biosensing. Meanwhile, the planewave coupled, multimode fiber and fiber
sidewall SPR counterparts are extensively employed for label-free biosensing.
In this paper, we report the design, fabrication and characterization of a
plasmonic crystal cavity on a SMF end facet, which shows high performance
label-free sensing capability that comes from a steep cavity resonance near the
plasmonic bandedge. The experimental figure-of-merit is 68 RIU^-1, which is
over twenty times improvement to previous reports. The refractive index
detection limit is 3.5*10^-6 RIU at 1 s integration time. We also describe a
novel glue-and-strip process to transfer gold nano structures onto fiber end
facets.Comment: 18pages, 5 figure
PT-Symmetric Phonon Laser
By exploiting recent developments associated with coupled microcavities, we
introduce the concept of PT-symmetric phonon laser with balanced gain and loss.
This is accomplished by introducing gain to one of the microcavities such that
it balances the passive loss of the other. In the vicinity of the gain-loss
balance, a strong nonlinear relation emerges between the intracavity photon
intensity and the input power. This then leads to a giant enhancement of both
optical pressure and mechanical gain, resulting in a highly efficient
phonon-lasing action. These results provide a promising approach for
manipulating optomechanical systems through PT-symmetric concepts. Potential
applications range from enhancing mechanical cooling to designing phonon-laser
amplifiers.Comment: 8pages, 7 figure
X(3872) as a molecular state in the Bethe-Salpeter equation approach
We discuss the possibility that the X(3872) can be a molecular
bound state in the Bethe-Salpeter equation approach in the ladder and
instantaneous approximations. We show that the bound state with
quantum numbers exists. We also calculate the decay width of
channel and compare our result with those
from previous calculations.Comment: 18pages,4 figure
Study of localized violation in and the branching ratio of in the QCD factorization approach
In this work, within the QCD factorization approach, we study the localized
integrated violation in the decay and the
branching fraction of the decay. Both the resonance
and nonresonance contributions are included when we study the localized
asymmetry in the decay. The resonance
contributions from the scalar and vector mesons are
included. For the meson, we apply both the Breit-Wigner and Bugg
models to deal with its propagator, and obtain and in these two models, respectively. We
find that there is no allowed divergence parameters and to
satisfy the experimental data
in the region
and
and the upper limit of
in the Breit-Wigner model,
however, there exists the region and satisfying the data for and
the upper limit of in the Bugg
model. This reveals that the Bugg model is more plausible than the Breit-Wigner
model to describe the propagator of the meson even though the
finite width effects are considered in both models. The large values of
indicate that the contributions from weak annihilation and hard
spectator scattering processes are both large, especially, the weak
annihilation contribution should not be negleted for decays to final states
including a scalar meson.Comment: arXiv admin note: substantial text overlap with arXiv:1811.0216
Quantum theory of photonic crystals
In this paper, we have firstly presented a new quantum theory to study
one-dimensional photonic crystals. We give the quantum transform matrix,
quantum dispersion relation and quantum transmissivity, and compare them with
the classical dispersion relation and classical transmissivity. By the
calculation, we find the classical and quantum dispersion relation and
transmissivity are identical. The new approach can be studied two-dimensional
and three-dimensional photonic crystals
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